Process for producing an oil seal to be applied to the rotary piston engine

ABSTRACT

A process for producing an oil seal for use in a rotary piston engine, which comprises the steps of forming an inner peripheral surface of an oil seal base body into an angled circumferential surface with a solid angle of 2 theta from a sliding surface side of the body toward a rear surface side or into an indented circumferential surface, cutting out partly the inner peripheral surface on the rear surface side along the inner peripheral surface, plating a hard metal layer on the slant or indented inner circumferential surface, and then honing exclusively a partial zone of the hard layer surface on the sliding surface side.

United States Patent 1191 Minegishi [111 3,824,662 1451 July 23, 1974 1 PROCESS FOR PRODUCING AN OIL SEAL TO BE APPLIED TO THE ROTARY PISTON ENGINE lnventor: Hiroshi Minegishi, Kawagoe, Japan Assignees: Nippon Piston Ring Co., Ltd.,

Tokyo; Toyo Kogyo Company Limited, Hiroshima-ken, both of,

Primary Examiner-Charles W. Lanham Assistant Examiner-D. C. Crane Japan Attorney, Agent, or FirmSughrue, Rothwell, Mion, [22] Filed: Feb. 8, 1972 Zinn & Macpeak [21] Appl. No.: 224,551 [57] ABSTRACT T A process for producing an oil seal for use in a rotary [30] Foreign Application Priority Data piston engine, which comprises the steps of forming an Feb. 8, 1971 Japan 46-4739 inner p ip Surface of an Oil seal base y into anangled circumferentialsurface with a solid ar glegf [52] US. Cl. 29/156.6, 277/96 R, 277/81 R 2 0 from a sliding surfa e side of the body toward a [51] Int. Cl B23p 15/06 ear surface side or into an indented circumferential [58] Field of Search 29/ 156.6, 156.63, 527.2; face, cutting out partly the inner peripheral surface 277/95, 96 R, 96 A, 81 R on the rear surface side along the inner peripheral surface, plating a hard metal layer on the slant or in- [56] References Cit d dented inner circumferential surface, and then honing UNITED STATES PATENTS exclusiyely a partial zone of the hard layer surface on 2,380,654 7/1945 Lane et al 29/l56.6 the Shdmg surface 3,218,086 1 H1965 Donley 277/96 R 3 Claims, 21 Drawing Figures a b 3 I 35 551 J 33 PATENIEB 3.824.662

SHEEI 2 BF 5 F|G.3A FIG. 38 FIG. 3C

PAINTED- 3.824.662

SHEEI 3 0? 5 FIG. 4B FIG. 4c

' I I BI 35 FIG. 5 FIG. 58 FIG. 5c

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention pertains to a process for producing an improved seal for use with rotary piston engines for sealing the sides of the rotary piston relative to the side of the piston housing to prevent the passage of lubricating oil into the combustion-chamber.

2. Description of the Prior Art As well known, the purpose of the oil seal used in a rotary piston engine is to maintain an oil-tight relationship between a stationary side housing and a rotor. The oil seal is generally composed of a radially inner oil seal and a radially outer oil seal each being assembled with an O-ring in a U-shaped channel formed in the seal and a spring for biasing the ring into engagement with the side housing. This oil seal assembly is applied to an oil seal groove in the rotor.

When proper oil-tightness between the side housing and the rotor is not fully obtained by the oil seal assembly, consumption of the lubricating oil increases, with unforeseen problems arising in the engine operation caused by carbon sludge which is produced by the combustion of the lubricating oil flowing into the combustion chamber. 7 Many investigations and developments on the oil seal have been carried out in order to eliminate the abovementioned defects. One improved oil seal assembly construction shown in FIGS. 1, 2C and 3C, has the radially. inner peripheral surface 32 of the oil seal 3 or 4 coated with a very hard metal layer 33, e.g., a hard Cr plated layer, a Mo sprayed or a nitrided layer, with the sliding surface 31 facing to the side housing 1 being formed at an angled surface 311 inclining with a rip angle of a from an edge 341 of the radially inner peripheral surface 32 on the sliding surface side and increasing towards the radially outer peripheral surface side. The edge 341 of the hard metal coated layer 33 therefore slides on an inner wall face of the side ho using 1 while maintaining intimate contact with the face 7 during the rotation of the rotor 2.

The width of the contact area between the oil seal of this type and the inner wall face of the side housing is always kept constant and does not exceed the thickness of the hard metal coated layer, due to an abrasion difference between the oil seal base body and the hard metal coated layer caused by the hardness difference between them. Accordingly, the oil-tightness between the side housing 1 and the rotor 2 is favorably maintained.

The process for producing this improved oil seal for rotary piston engines has one major drawback, however. Since the manufacturing steps include a preliminary step for forming a base metal into an oil seal base body, a plating step for providing a hard metal layer on the radially inner peripheral surface of the oil seal base body, a honing step for smoothing the rough surface of the plated hard metal layer into a fine smooth surface, and a finishing step for obtaining the final desired shape of the oil seal, including the rip cutting of the angled side, a considerable increase in manufacturing time is required. Specifically, the honing treatment step applied to the entire surface of the plated hard metal layer generally requires 16-20 minutes. Consequently, this increase in time raises the cost of the oil seal product.

SUMMARY OF THE INVENTION An object of this invention is to provide a novel process for producing an oil seal for a rotary engine and which decreases the time required for honing the plated hard metal surface layer and thus reduces the cost of the resulting oil seal product.

According to the process of this invention, the preliminary working comprises the steps of forming the radially inner peripheral surface of the oil seal base body into an angled planar surface forming a predetermined angle, designated as 20 with the sliding surface side of the body towards the rear surface side of the same or into an indented circumferential surface partially cut outof the radially inner peripheral surface on the rear surface side, leaving a zone extending along the radially inner peripheral surface. The honing treatment step is applied exclusively to the surface of the plated hard metal layer provided on the sliding surface zone side.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a partly enlarged vertical crosssectional view of an oil seal assembly assembled in a rotary piston engine;

FIGS. 2A, 2B and 2C are vertical cross-sectional views of a conventional inner oil seal, showing the sequential steps for producing the oil seal and its base body;

FIGS. 3A, 3B and 3C are vertical cross-sectional views of a conventional outer oil seal, showing the sequential steps for producing the oil seal and its base body;

FIGS. 4A, 4B and 4C are explanatory views of the steps of a process for producing an inner oil seal according to this invention, showing vertical cross sections of the oil seal and its base body;

FIGS. 5A, SB and 5C are explanatory views of the steps of a process for producing an outer oil seal according to this invention, showing vertical cross sections of the oil seal and its base body;

FIGS. 6A and 6B are graphs comparing the sealing ability of a conventional oil seal assembly shown in FIGS. 2C and 3C with that of the oil seal assembly of this invention shown in FIGS. 4C and 5C;

FIGS. 7A, 7B and 7C are explanatory sectional views of an oil seal, showing a process for producing a second DESCRIPTION OF PERFERRED EMBODIMENTS The preferred embodiments of the present invention will now be described with reference to the accompanying drawings. As seen in FIG. 1, a rotary piston engine has a stationary housing 1, within which a piston 2 rotates. An oil seal assembly consisting of an inner oil seal 3 and an outer oil seal 4 is located in slots or grooves 21 cut in the sides of the rotary piston 2 around the axis of rotation thereof.

A radially inner peripheral surface 32 of the inner oil seal base body is formed at an angle 0 relative to the central axis of the ring, the angled circumferential surface 321 forming a solid angle of 20 from the side of sliding surface 31 toward the side of rear surface 35 as shown ill'FlG. 4A. The surface 321 is provided with a Cr layer 33 by plating as shown in FIG. 4B-with the surface of Cr plated layer also slanting substantially equal to the surface 321. Thereafter, a honing treatment for making the Cr plated layer surface into a fine smooth surface is applied exclusively to a partial zone of the Cr plated layer surface 331 extending along the inner periphery of theoil seal with a width of I from the edge of the surface 341 on the side of sliding surface 31 as shown in the FIG. 4C. The sliding surface 31 may be cut at an angle a relative to the perpendicular plane as described above in the prior art, if desired.

The radially inner peripheral surface of the outer oil seal base body 4 is formed into a stepped circumferential surface having two inner peripheral surfaces 32a and 32b of different diameters at both sides of the inner peripheral surface. The outer-most surface 32a has a width of I from the edge of said inner peripheral surface 31 on the sliding surface side, and the inner-most surface 32b on the side of rear surface 35 is formed into a recessed surface 32lb by cutting out the surface 32b with a depth of h from the diameter of surface 32a along the surface 32bas shown in FIG. 5A. Both surfaces 32a and 32lb are then, provided with Cr layers 33a and 33b respectively by plating as shown in FIG. 5B, and thereafter the honing treatment is applied exclusively to a surface 331a of the formerCr plated layer 330 on the side of the sliding surface 31 as shown in FIG. 5C.

According to the above described processes of this invention, the time required for honing is greatly reduced as compared with the conventional processes.

The sealing ability of this special oil seal will be compared in the following tables and in FIGS. 6A and 68 with that of the conventional oil seal rings. Generally, the oil sealing ability of an oil seal is determined on the basis of the consumption of the lubricating oil during actual engine operation.

FIGS. 6A and 6B show graphs comparing the amount of lubricating oils consumed in a rotary piston engine with the oil seal of this invention with that of the conventional oil seal.

The values for 0, l and h of the oil seal of this invention used in the test for the lubricating oil consumption are shown in Table 1 below:

TABLE I Outer oil Seal Ring Inner Oil Seal Ring h 0.1 mm 0 2 L is the width of the inner peripheral surface of the oil seal ring Total exhaustion volume or displacement maximum output maximum torque compression ratio mops/7.000 rpm. 135 kg'm/3.000 rpm. 9.4:l

Plain columns A in FIGS. 6A andy6B show the test results on the conventional oil seal assembly composed of the inner oil seal shown in FIG. 2C and the outer oil seal shown in FIG. 3C, when applied to above said MIOA type rotary engine, whereas cross-hatched columns B in FIGS. 6A and 6B show the test results on the oil seal assembly constructed according to the process of this invention composed of the inner and outer oil seal shown in FIGS. 4C and 5C respectively and Table l.

The conditions for operating the MIOA type rotary engine are shown in Table 3.

50 ps load/6500 r.p.m.

It is apparent from FIGS. 6A and 68 that almost equal lubricating oil consumptions are obtained with use of the conventional oil seal and the novel oil seal ring of the present invention. Therefore, the present invention provides an oil seal having favorable oil sealing qualities quite comparable with that of the conventional oil seal, while being produced at lower cost due to the reduction of time required for the honing treatment step. 7

The optimum ranges obtained by many tests in which the solid angle 26 of the radially inner circumferential surface, the depth it cut out of the inner peripheral surface on the rear surface side, and the width l of the Cr plated layer surface to be subjected to the honing treatment were changed as follows:

l /3 of the entire width L of the inner peripheral surface of the oil seal h 0.1 mm A of the depth of the groove in which is inserted an O ring 5 As a result of the tests, the process of the present invention brings about a reduction in the time required for honing to approximately 6-8 minutes.

Thus, an oil seal having an equally favorable oil sealing ability as that of the conventional oil seal can be manufactured in a shorter period of time. and with lower cost by applying the process of this invention.

Although this invention has been described with regard to an oil seal having the radially inner peripheral surface plated with Cr layer, it will be understood to one skilled in the art that the layer will not be restricted only to a Cr plated layer but may be any one of the hard metallic layers, such as M0 sprayed layer, surface nitrided layer and the like.

Although an exemplified embodiment of this invention has been described with reference to the radially inner oil seal having an angled radially inner circumferential surface as shown in FIGS. 4A 4C and the radially outer oil seal having the indented inner peripheral surface as shown in the FIGS. 5A 5C, the radially inner angled circumferential surface and the radially inner indented circumferential surface can be duly applied to the inner oil seal and the outer oil seal, respec- 6 tively, as shown in FIGS. 7A to 7C and FIGS. 8A to SC honing a predetermined width of a partial zone of without varying from the scop o this invention said hard metal layer surface from the edge of said 1 Claim? layer on the sliding surface side to a predetermined A Process Producing an oil S eal for f a diameter to forma fine hard metal surface at the tary piston internal combustion engine comprising the 5 partial zone steps of:

formin an inner eri heral surface of an oil seal base O o body into an a gle circumferential surface slantdetermmed angle a range 9 1 45 ing radially outwardly from a sliding surface side of A W accPrfimg to Clam] 531d Pf said base body towards a rear surface thereof with 10 detel'mmed Wldth m range of V of the entire a predetermined angle, applying a layer f h d width of the inner peripheral surface of the oil seal. metal to said angled circumferential surface, and

2. A process according to claim 1, wherein said pre- 

1. A process for producing an oil seal for use in a rotary piston internal combustion engine comprising the steps of: forming an inner peripheral surface of an oil seal base body into an angled circumferential surface slanting radially outwardly from a sliding surface side of said base body towards a rear surface thereof with a predetermined angle, applying a layer of hard metal to said angled circumferential surface, and honing a predetermined width of a partial zone of said hard metal layer surface from the edge of said layer on the sliding surface side to a predetermined diameter to form a fine hard metal surface at the partial zone.
 2. A process according to claim 1, wherein said predetermined angle is in a range of 1* 45'' - 2* 15''.
 3. A process according to claim 1, wherein said predetermined width is in a range of 1/4 - 1/3 of the entire width of the inner peripheral surface of the oil seal. 